This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to Patent Application Serial No. 0101565-0 filed in Sweden on May 7, 2001, the entire content of which is hereby incorporated by reference.
This invention relates to a tool intended for chip removing machining, including a holder having a seat formed in a first side for a cutting insert of the type that includes a hole for clamping the same. The clamping is performed by means of a clamping mechanism that comprises a clamping body provided with a finger, which is movable backwards and forwards inside a cavity in the interior of the holder and cooperates with a screw arranged in a bore formed in the holder. The bore ports in a second side of the holder, distanced from said first side, with the purpose of enabling access to the screw from a direction other than from the first side along which the seat is located. The screw is formed with a thick, first portion, as well as a thinner, second portion, having a male thread which is in engagement with a female thread in a through hole in the clamping body.
Tools of the kind in question are used primarily for the machining, in particular turning, of metallic work pieces.
A chip removing tool or cutting tool of the above-mentioned type is previously known from the Japanese patent application JP 2000-254 806. Generally characteristic of this known cutting tool is that the holder for the cutting insert has the shape of a long narrow, cross-section-wise quadrangular shaft in which the seat for the cutting insert is formed in a first side (top side) of the four sides that define the shaft. More precisely, the seat is placed in connection with an acutely angled corner at a front end of the shaft. In this case, a cavity for the clamping body is formed in a linear extension of a threaded bore for a screw for tightening the clamping body. In other words, the cavity and the threaded bore form a through hole, porting in two parallel sides, extending perpendicularly to the first side in which the seat is formed. In the embodiment example according to said Japanese patent application, the through hole extends at an acute angle (approx. 60xc2x0) to the longitudinal axis of the shaft. The clamping body is cylindrical and has a central through hole with a female thread. The tightening screw is formed with two male threads, viz., a first male thread that is formed on a thick, first portion of the screw and is in engagement with a female thread in said bore in the shaft, and a second male thread that is formed on a second, thinner portion of the screw and is in engagement with said female thread inside the clamping body. At the end of the thick portion of the screw, accessible from the outside, a socket for a spanner is present. Clamping of the cutting insert in the seat is carried out by tightening the screw in the clamping body. Release of the cutting insert is achieved by the screw being screwed out from the clamping body. Thanks to the fact that one of the male threads (together with the appurtenant female thread) is left hand-threaded and the other male thread (together with the appurtenant female thread) is right hand-threaded, clamping and release, respectively, of the cutting insert may be effected quickly.
A substantial advantage of the known cutting tool is that the screw for clamping the cutting insert is accessible from a side of the shaft or holder other than the side in which the cutting insert is mounted. Thus, the spanner for the screw does not need to be inserted into the spanner socket of the screw from the topside of the cutting insert, such as the case is in conventional cutting tools. In this way, a plurality of cutting tools can be mounted very near each other in a machine.
However, the cutting tool known from JP 2000-254 806 is also associated with disadvantages. One disadvantage is that the cavity for the clamping body is open in the side of the shaft opposite the screw bore, whereby the clamping body is inserted from that opposite side while the finger on the clamping body passes through an open slot formed in the bottom of the cutting seat. This means that the support of the cutting insert against the bottom surface of the seat becomes unsatisfactory. When the cutting insert, during operation, is exposed to stresses, the thin-material portions on both sides of the slot for the finger may give way. Furthermore, the cutting insert completely lacks support in the area of the outer end of the slot. Another disadvantage is that the screw after a certain time of usage, risks being deformed by bending in connection with the repetitive clamping operations, since only one end of the screw is actually supported, i.e., the screw is supported in cantilever fashion. An additional disadvantage of the known construction is that the same includes no less than four threads, viz. two male threads on the screw and two female threads (in the bore in the shaft and the hole in the clamping body, respectively). To produce threads is a generally cost-demanding machining operation which entails that the cutting tool in its entirety becomes expensive to manufacture.
The present invention aims at obviating the above-mentioned disadvantages of the previously known cutting tool and at providing an improved cutting tool. Therefore, a primary aim of the invention is to provide a cutting tool that guarantees a satisfactory support for the cutting insert in spite of the existence of a cavity for a clamping body beneath the bottom of the cutting insert. Another aim of the invention is to minimise the risk of bending deformations in the screw and clamping body, respectively. Yet another aim is to provide a cutting tool, the clamping body of which is controlled in such a way in the cavity that the finger engaging in the hole of the cutting insert does not tilt. In other words, the finger should in a reliable way always be pressed against one and the same contact place in the hole in the cutting insert. It is also an aim to minimise the number of threads, with the purpose of reducing the total cost for the manufacture of the cutting tool, as well as guaranteeing an optimum precision in the movements of the clamping body and the screw.
According to the invention, at least the primary aim is attained by a tool for chip removing machining which comprises a holder that includes first, second, third, and fourth sides. An insert seat is formed in the first side for receiving a cutting insert. The seat includes a bottom surface and an upright support surface. The bottom surface includes a hole formed therethrough. The second side is disposed opposite the first side. Each of the third and fourth sides interconnects the first and second sides, with the fourth side disposed opposite the third side. A cavity is formed within the holder and communicates with the cavity. A bore extends from the third side toward the fourth side and communicates with the cavity. The bore is spaced from the first side. A clamping body is disposed in the cavity and is movable in a direction parallel to a center axis of the bore. The clamping body includes a through-hole extending along the center axis. The through-hole includes a female screw thread. A finger projects from the clamping body and extends through the hole, the hole being of larger cross-section than the finger. A rotatable screw is provided which includes first and second ends and an intermediate portion. The first end is disposed in the bore. The intermediate portion is disposed within the through-hole of the clamping body and includes a male screw thread in threaded engagement with the female screw thread. The second end is supported by an end wall defined by the fourth side. The finger is completely surrounded by the bottom surface of the insert seat.